@misc{indiciae30b108d2f207,
  title = {Twenty years ago.},
  author = {P J Helliwell and A M Hutton},
  year = {1968},
  doi = {10.1111/j.1365-2044.1968.tb00136.x},
  url = {https://pubmed.ncbi.nlm.nih.gov/4877722/},
  note = {Source identifier: 4877722}
}